In reply to Kemics:
I got an email/newsletter from a camera shop the other day and there was an ad saying the Fuji double cashback offer which they did for Black Friday is being repeated on boxing day.
So don't buy the XT10 before then if that's what you decide to go for. There is an £80 trade in bonus offer as well (until 31/12) I am assuming you cannot use both at the same time though?
I got a Sony Nex 5 when they first came out and although I liked it, I found the lens choice a bit limited and some of the lenses a bit big. Now own an EM10 (original model) and like that a lot - it feels more 'fun' to use than the Nex, more physical controls etc. Also has a decent choice of good lenses including some at fairly low prices- Sigma 19mm and 30mm for example (£120) as well as some very compact lenses like the 20mm Panasonic , 12-32 Panasonic, 35-100 Panasonic and the Olympus 9-18. (I have the latter lens and the 20mm pancake). I find the camera much easier to use with the optional extra grip. Olympus EM10 mkii is good value at the moment with the cashback as the price has dropped since launch with it being out for a while.
Fuji cameras look great, but again some of the lenses are quite large relative to the smaller bodies and prices quite high too. The 27mm f2.8 pancake looks like a similar lens to the Panasonic 20mm on m43 and is fairly inexpensive. The 16-50 kit is supposed to be pretty decent too for a kit lens and a bit wider than the usual 18-55.
RX100 if you want something really compact and don't want to change lenses, does decent video clips too (I have the original RX100 model, but would go for the mkii if I was buying again as I prefer the tilty screens).
Lots of good cameras around really - just depends what your priorities are (and budget) but if you want something that fits in a jacket pocket then I would say Sony a6000 / Fuji xt10 / Olympus em5ii/Em10ii will all only really fit in with a pancake lens on and even then you will certainly notice they are there.